Synthesis and dissolution behavior of β-TCP and HA/β-TCP composite powders

Calcium phosphate powders, β-TCP and biphasic HA/β-TCP, were synthesized by calcining the powders obtained from the co-precipitation method using Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄. The effects of the initial Ca/P ratio and pH of the solution on the phase evolution and in vitro dissolution behavior of the powders in a Ringer's solution were investigated. The Ca/P ratio of the resulting powders was strongly dependent on the pH of the solution and weakly dependent on the initial Ca/P ratio. Single phase TCP powder was obtained at pH=7.4 and the initial Ca/P ratio had a little effect on the resulting Ca/P ratio. Biphasic composite powders were prepared at pH=8.0 and the Ca/P ratio of resulting powder was controllable by adjusting the initial Ca/P ratio. TCP powder showed the highest dissolution rate in the Ringer's solution and biphasic composite powder exhibited an intermediate dissolution behavior between that of HA and TCP.     

Synthesis and characterisation of β-TCP/bioglass/zirconia scaffolds

Tricalcium phosphate scaffolds reinforced with bioglass were characterised morphologically, physically, and mechanically. The scaffolds were fabricated through powder technology and the polymer foaming technique using 80?wt-% of β-TCP and 20?wt-% of phosphate-based bioglass doped with zirconia in various amounts (0, 0.25, 0.5, 0.75, and 1.0?wt-%). The foaming agent was varied (1, 1.5, 2, 2.5, and 3?wt-%) to determine the optimal amount that ensured an interconnected porosity and pore size suitable for increasing osteoconduction and cell attachment. Promising samples for tissue engineering applications showed a pore size ranging from 1.41 to 303?μm, total porosity of 50–53%, compressive strength values between 0.6 and 1?MPa, Young’s modulus from 357 to 574?MPa, and excellent interconnectivity.     

Synthesis,characterization and controlled release properties of zinc–aluminium-beta-naphthoxyacetate nanocomposite

An organic–inorganic nanohybrid nanocomposite was synthesized by co-precipitation method using beta-naphthoxyacetate (BNOA) as guest anion and zinc–aluminium layered double hydroxide (Zn–Al-LDH) as the inorganic host. A well-ordered nanohybrid nanocomposite was formed when the concentration of BNOA was 0.08 M and the molar ratio of Zn to Al, R = 2. Basal spacing of layered double hydroxide containing nitrate ions expanded from 8.9 to 19.5 Å in resulting of Zn–Al-BNOA nanocomposite was obtained indicates that beta-naphthoxyacetate was successfully intercalated into interlayer spaces of layered double hydroxide. It was also found out the BET surface area increased from 1.13 to 42.79 m² g^?1 for Zn–Al-LDH and Zn–Al-BNOA nanocomposite, respectively. The BJH average pore diameter of the synthesized nanocomposite is 199 Å which shows mesoporous-type of material. CHNS analysis shows the Zn–Al-BNOA nanocomposite material contains 36.2 % (w/w) of BNOA calculated based on the percentage of carbon in the sample. Release of BNOA from the lamella of Zn–Al-BNOA was controlled by the zeroth and first order kinetics at the beginning of the deintercalation process up to 200 min and controlled by pseudo-second order kinetics for the whole process. This study suggests that layered double hydroxide can be used as a carrier for organic acid herbicide controlled release formulation of BNOA.     

Mechanical properties,microstructure, and bioactivity of β-Si3N4/HA composite ceramics for bone reconstruction

Pure hydroxyapatite (HA) as bone graft substitute has excellent osteogenic activity, but it has lower fracture toughness and its biological activity is harmed by the addition of toughening phases, which limits its clinical application. To alleviate the contradiction, columnar β-Si₃N₄ as the toughening phase and La³⁺/Y³⁺ sintering aid as active ions are used in this study to prepare β-Si₃N₄/HA composite biomaterials. According to the results, hardness and toughness of 10 wt% β-Si₃N₄/HA composite prepared by cold press sintering at 1300 °C were 6.44 GPa and 1.69 MPa m^1/2, respectively, being 110% and 140% higher than those of pure HA. Moreover, 10 wt% β-Si₃N₄/HA composite exhibited better protein adsorption capacity and obviously stimulated adhesion, proliferation, and osteogenic differentiation of osteoblast. In addition, it was found that sintering aid not only facilitated the improvement of mechanical properties, but also promoted the formation of 100–200 nm nanostripe structure, which was beneficial to cell adhesion. Determination of La³⁺concentration combined with biological experiments also proved that its concentration range from 4×10⁻⁸ M to 6 × 10⁻⁸M was beneficial to cell proliferation and osteogenic differentiation. In summary, β-Si₃N₄ and sintering aids were shown to improve mechanical properties of HA at maintaining the biological activity of the latter.     

Synthesis and in vitro bioactivity assessment of injectable bioglass−organic pastes for bone tissue repair

The aim of this work was to study the bioactivity of systems based on a clinically tested bioactive glass (BG) particulates (mol%: 4.33 Na₂O−30.30 CaO−12.99 MgO−45.45 SiO₂−2.60 P₂O₅−4.33 CaF₂) and organic carriers. The cohesiveness of injectable bone graft products is of high relevance when filling complex volumetric bone defects. With this motivation behind, BG particulates with mean sizes within 11−14 μm were mixed in different proportions with glycerol (G) and polyethylene glycol (PEG) as organic carriers and the mixtures were fully injectable exhibiting Newtonian flow behaviors. The apatite forming ability was investigated using X-ray diffraction and field emission scanning electron microscopy under secondary electron mode after immersion of samples in simulated body fluid (SBF) for time durations varying between 12 h and 7 days. The results obtained revealed that in spite of the good adhesion of glycerol and PEG carriers to glass particles during preparation stage, they did not hinder the exposure of bioactive glass particulates to the direct contact with SBF solution. The results confirmed the excellent bioactivity in vitro for all compositions expressed by high biomineralization rates with the formation of crystalline hydroxyapatite being identified by XRD after 12 h of immersion in SBF solution.     

Synthesis of graphene–CNT hybrids via joule heating: Structural characterization and electrical transport

Graphene–CNT (G/CNT) hybrids were formed via in situ joule heating inside a transmission electron microscope (TEM). The formation of the G/CNT structure was suggested to be induced by the sequential and spontaneous unzipping of the outmost wall of the multi-walled CNT under uniformly thermal etching and voltage pulse of 0.2–1 V. The conductance of the G/CNT hybrids show a significantly change (up to 38 times) after decorated with CdTe quantum dots. Our results suggest the potential use of the G/CNT hybrids for high-sensitivity detections, as well as super capacitors or catalyst matrices given their large specific surface areas.     

Epoxy/polyaniline–ZnO nanorods hybrid nanocomposite coatings: Synthesis,characterization and corrosion protection performance of conducting paints

The objective of this research is the production of an epoxy coating blended with organic–inorganic hybrid nanocomposite as a corrosion inhibiting pigment applied over carbon steel grade ST37. A series of conducting polyaniline (PANI)–ZnO nanocomposites materials has been successfully prepared by an in situ chemical oxidative method of aniline monomers in the presence of ZnO nanorods with camphorsulfonic acid (CSA) and ammonium peroxydisulfate (APS) as surfactant and initiator, respectively. The synthesized polymers were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and electrical conductivity techniques. Synthesized nanocomposites were solved in tetraethylenpentamine (TEPA), and then prepared solution was mixed with epoxy and then was applied as a protective coating on carbon steel plates. The anti-corrosion behavior of the epoxy binder blended with PANI–ZnO nanocomposites were studied in 3.5% NaCl solution at a temperature of 25 °C by electrochemical techniques including electrochemical impedance spectroscopy (EIS) and chronopotentiometry at open circuit potential (OCP). It was observed that the epoxy coating containing conducting PANI–ZnO nanocomposites exhibited higher corrosion resistance and provided better barrier properties in the paint film in comparison with pure epoxy and epoxy/PANI coatings. In the case of conducting coatings, the OCP was shifted to the noble region due to presence of PANI pigments. Additionally, the possibility of formation of a passive film in the presence of PANI was reinforced at the substrate–coating interface. SEM studies taken from surface of the coatings showed that epoxy/PANI–ZnO hybrid nanocomposite coating systems (EPZ) are crack free, uniform and compact. Furthermore, it was found that the presence of ZnO nanorods beside PANI can significantly improve the barrier and corrosion protection performance of the epoxy coating due to the flaky shaped structure of the PANI–ZnO nanocomposites.     

Antibacterial properties,in vitro bioactivity and cell proliferation of titania–wollastonite composites

Titania–wollastonite materials that show high in vitro bioactivity, appropriate cell proliferation and antibacterial behavior have been developed. Titania–wollastonite compounds were synthesized by two different routes: (i) solid state reaction and (ii) sol–gel. The in vitro bioactivity assessment was performed by immersing samples in a simulated body fluid (SBF). The materials characterization, before and after immersion in SBF, was performed by SEM and EDS. Cytotoxicity was assessed by estimating cell proliferation and the antibacterial properties were evaluated by performing a kinetic study of a bacterium growth (Burkhoderia cepacia). In order to evaluate the band gap value UV–vis spectroscopy was performed. A faster apatite layer formation was observed on the samples processed by sol–gel. However, these agglomerates were smaller than those formed on the solid state reaction substrates. The highest inhibition of the bacteria growth and the highest cell proliferation were observed on the samples synthesized by solid state reaction.     

Synthesis,in vitro Antileishmanial Efficacy and Hit/Lead Identification of Nitrofurantoin-Triazole Hybrids

Leishmaniasis is a vector-borne neglected parasitic infection affecting thousands of individuals, mostly among populations in low- to moderate-income developing countries. In the absence of protective vaccines, the management of the disease banks solely on chemotherapy. However, the clinical usefulness of current antileishmanial drugs is threatened by their toxicity and the emergence of multidrug-resistant strains of the causative pathogens. This emphasizes the imperative for the development of new and effective antileishmanial agents. In this regard, we synthesized and evaluated in vitro the antileishmanial activity and cytotoxicity profile of a series of nitrofurantoin-triazole hybrids. The nitrofurantoin derivative 1 featuring propargyl moiety was distinctively the most active of all, was nontoxic to human cells and possessed submicromolar cellular activity selectively directed towards the pathogens of the life threatening visceral leishmaniasis. Hence it was identified as potential antileishmanial lead for further investigation into its prospective to act as alternative to therapies.     

Improved properties of hydroxyapatite–carbon nanotube biocomposite: Mechanical,in vitro bioactivity and biological studies

The present work describes a simple shear mixing technique for developing a hydroxyapatite (HAp)–carbon nanotube (CNT) nanocomposite and the effect of reinforcement on the physical, mechanical, in vitro bioactivity and biological properties of HAp. XRD and FTIR confirmed that the main phase of the composites is HAp. HRTEM images demonstrated the formation of a two-dimensional nanocomposite structure, whereas FESEM images indicated the formation of nanosized HAp grains featuring sporadically distributed CNT molecules. No major phase changes in HAp were observed with up to 5% added CNT. However, adding more than 1% CNTs caused an increase in internal crystal strain and increased substitution of CO₃²⁻ for OH⁻ and PO₄³⁻ groups in pure HAp. The average crystallite size increased from ~46 nm to ~100 nm with only 0.5% added CNT, remained nearly unaffected up to 2% CNTs thereafter and suddenly decreased at 5% CNTs (~61 nm). The FESEM and HRTEM images clearly showed the attachment of MWCNT chains on HAp grains, which directly affected the samples' fracture toughness and flexural strength. Of the samples, 1% showed maximum values of K_1C, whereas 5% showed maximum values of HV and three-point bending flexural strength. The in vitro bioactivity indicated increased apatite formation on the sample surface up to 1% CNTs after 24 weeks. However, adding 2% and 5% CNTs resulted in a manifold increase in apatite formation up to 12 weeks, after which dissolution increased up to 24 weeks, possibly due to increased substitution of CO₃²⁻ for OH⁻ and PO₄³⁻ groups. This result is confirmed by the FTIR studies. For all added CNT contents, all samples exhibited high haemocompatibility. However, there was a compromise between the observed mechanical properties and in vitro bioactivity studied up to 24 weeks, and care must be taken before selecting any final application of the nanocomposites.     

Synthesis,characterization, and infrared-emissivity study of Ni–P–CB nanocomposite coatings by electroless process

The Ni–P–CB (carbon black) nanocomposite coatings have been successfully deposited on an ABS plastic matrix via electroless plating process. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectrometry techniques were employed to examine the surface morphology and structure of the as-plated coating. Energy dispersive spectroscopy (EDS) was adopted to obtain the component analysis of the Ni–P–CB composite coating, and the infrared emissivity of the coating was determined by the IRE-I Infrared Emissometer. SEM and XRD results indicated that the nanoparticles were dispersed homogeneously in the Ni–P coating; the result of EDS showed that the increased rate of CB content is in correspondence with its concentration. In the case that CB concentration is lower than 4 g/L, the increase rate is sharp, whereas when the concentration is higher than 4 g/L, the increase rate is reduced significantly. Furthermore, study of infrared emissivity shows that the nanocomposite coatings possessed low emissivity value. A comparison of the infrared emissivity dependence on surface resistivity obtained from the analysis of the experimental results and those calculated using the Hagen–Rubens relation indicates that the Hagen–Rubens relation is good for modeling the infrared emissivity of the Ni–P–CB nanocomposite coatings.     

Polymerization of β-cyclodextrin with 1,2,3,4-butanetetracarboxylic dianhydride: Synthesis,structural characterization,and bisphenol A adsorption capacity

Water-soluble and water-insoluble β-cyclodextrin polymers (β-CDPs) were prepared from β-CD using 1,2,3,4-butanetetracarboxylic dianhydride (BTCA) as a cross-linker. The structures of the synthesized water-soluble and water-insoluble β-CDPs were characterized in detail using FT-IR, solution- and solid-state NMR, and ¹H diffusion-ordered spectroscopic techniques. The water solubility of β-CDP was dependent on the reaction temperature as well as the initial feed ratio of β-CD and BTCA. The BTCA content and the ratio of BTCA molecules cross-linked and grafted to β-CD were also found to influence the water solubility of the polymers. Insoluble β-CDPs were effective in adsorbing bisphenol A (BPA) from aqueous media, with this absorption being highest in materials of low BTCA content, which corresponds to material of high β-CD content per unit mass of β-CDP.     

Design,Synthesis, and in vitro Evaluation of P2X7 Antagonists

The P2X7 receptor is a promising target for the treatment of various diseases due to its significant role in inflammation and immune cell signaling. This work describes the design, synthesis, and in vitro evaluation of a series of novel derivatives bearing diverse scaffolds as potent P2X7 antagonists. Our approach was based on structural modifications of reported (adamantan-1-yl)methylbenzamides able to inhibit the receptor activation. The adamantane moieties and the amide bond were replaced, and the replacements were evaluated by a ligand-based pharmacophore model. The antagonistic potency of the synthesized analogues was assessed by two-electrode voltage clamp experiments, using Xenopus laevis oocytes that express the human P2X7 receptor. SAR studies suggested that the replacement of the adamantane ring by an aryl-cyclohexyl moiety afforded the most potent antagonists against the activation of the P2X7 cation channel, with analogue 2-chloro-N-[1-(3-(nitrooxymethyl)phenyl)cyclohexyl)methyl]benzamide ( 56 ) exhibiting the best potency with an IC₅₀ value of 0.39 μM.     

Enhanced in vitro inhibition of MCF-7 and magnetic properties of cobalt incorporated calcium phosphate (HAp and β-TCP) nanoparticles

The Co²⁺ (0.1 M) incorporated hydroxyapatite (HAp) and beta tricalcium phosphate (β-TCP) nanoparticles were synthesized by the microwave assisted technique and sintering of HAp respectively. The samples were thermally treated at temperatures ranging from 200 to 1000°C. The partial substitutions of Co²⁺ at the Ca²⁺ site of HAp were confirmed from the slight shift (～0.2°) in the (002) and (211) XRD peaks. The morphology of the nanoparticles was transformed from nanospheres to twinned particles on thermal treatment. In addition, the particle size of Co-600 was increased (from ～50 nm to ～100 nm) due to the recrystallization process. Further, the thermal treatment enhanced the crystallinity (41.15 to 90.16%), retentivity (M_r) and coercivity (H_c) of the nanoparticles. The cobalt incorporated HAp and β-TCP possessed paramagnetic property. The excellent bioactivity of β-TCP has been confirmed by the mineralization in simulated body fluid (SBF). Compared to HAp, β-TCP possessed better compatibility towards C2C12 cells on cobalt incorporation as evidenced by the in vitro cell viability. Moreover, both HAp and β-TCP have significantly inhibited the growth of MCF-7 on increasing the interaction time (72 h). Hence, the inhibition characteristics of Co²⁺ incorporated calcium phosphate (CaP) towards MCF-7 (without affecting the normal cells) demonstrate its competency as a potential material for cancer therapy over the already existing nanoparticles.     

Synthesis of β-TCP and CPP containing biphasic calcium phosphates by a robust technique

Biphasic calcium phosphate (BCP) compositions consisting of β-tricalcium phosphate (β-TCP) and calcium pyrophosphate (CPP) are potential biodegradable ceramics for bone regeneration. The present work demonstrates the formation of such dense ceramics by first preparing the precursors of nano-sized, amorphous, and equiaxed calcium pyrophosphate particles, and then sintering the precursors at 900 °C to transform them into desired BCP. However, if the complex of calcium tripolyphosphate was used, only CPP could be generated. It was also observed that the incorporation of Mg²⁺ had several effects on the resulting products including: (1) promoting the generation of meso-porous precipitates; (2) favoring the formation of β-TCP instead of CPP; (3) reducing the grain size and increasing the density of the sintered ceramics, and (4) enhancing the negative electric charge of the BCP surface. Thus, the as-prepared BCP ceramics can serve as potential bone substitute materials in orthopedic applications.     

Mullite/ β-spodumene composites: Preparation and characterization

Mullite/ β-spodumene composites were fabricated by the addition of 5 up to 20 mass% β -spodumene powder to mullite matrix. Both mullite and β-spodumene were prepared by sol-gel technique. The batches were uniaxially pressed into discs and rectangular bars, then pressureless sintered at 1400 °C up to 1700 °C for 1 h. Mechanical and thermal properties, as well as microstructure and phase composition were carried out on the sintered composites. The results show that although the increase in the soft β-spodumene reduces the hardness and the thermal expansion of the composites, they lower the firing temperature and enhance the flexural strength. The study indicates that β-spodumene content has a noticeable effect on the composites thermal expansion coefficient. It also shows that it is possible to tailor mullite/ β-spodumene composite with adjusted thermal expansion coefficient by changing the mullite to β-spodumene ratio.     

Synthesis of dysprosium/Mn–Cu ferrite binary nanocomposite: Analysis of structural,morphological, dielectric,and optomagnetic properties

Manganese–copper ferrite (MCFO) and dysprosium (Dy)-doped manganese–copper ferrite nanocomposites (Mn_0.5Cu_0.5Dy_xFe_2−xO₄) (x = 0, 0.05, 0.10, and 0.15) were synthesized by sonochemical method. Crystal structure and the structural parameters of the MCFO were analyzed based on the doping concentration of Dy ion. It was observed that the average crystalline size of the synthesized nanocomposite decreases when the concentration of Dy increases. The existing spherical surface morphology of the MCFO and Dy-doped MCFO nanocomposites were obtained through scanning electron microscopy. In the UV spectrum, the pristine MCFO sample showed an absorbance peak at 743 nm whereas the absorbance values of Dy-doped ferrite nanocomposite considerably shifted (blue) toward a lower wavelength (231–222 nm). The dielectric parameters of all ferrite nanocomposites were studied in the frequency range of 100 Hz to 5 MHz. The dielectric spectrum revealed that dielectric constant and loss tangent decreased with increased doping concentration of Dy ion. The saturation magnetization also changed with Dy doping in MCFO. The impact of Dy on manganese–copper ferrite changed the optical, dielectric and magnetic properties of the prepared binary ferrite nanocomposite, which can be used for microwave-absorbing material applications.     

Synthesis,characterization, and magnetic properties of α-MnS nanocrystals

MnS nanocrystals have been prepared by a colloidal synthesis route through the reaction of MnCl₂ and S[Si(CH₃)₃]₂ in trioctylphosphineoxide. The nanocrystals were characterized using X-ray diffraction and transmission electron microscopy. The magnetic properties were studied with SQUID magnetometry. X-ray diffraction shows that the nanocrystals are of the thermodynamically stable α-MnS (alabandite) structure. Size control was achieved by changing the concentration of the precursors. Nanocrystal sizes were measured by transmission electron microscopy, and three samples of average diameters 20, 40, and 80 nm were obtained, with narrow size distribution (σ˜9%). The zero field cooled magnetization curves for the 80-, 40-, and 20-nm samples showed a cusp at 116 K, 97 K, and 50 K respectively, all smaller than the antiferromagnetic transition temperature, T_N = 130 K, of bulk α-MnS. Below T_N the magnetization exhibits a paramagnetic behavior unlike typical antiferromagnetic materials. These results indicate that there is a mixture of paramagnetic and antiferromagnetic phases in the nanocrystals. The size dependence shows a general trend of decrease of T_N with reduced particle size, indicating size dependent magnetic ordering.     

Phase Transition from α-TCP into β-TCP in TCP/HA Composites

The phase transition from α-tricalcium phosphate (α-TCP) into β-tricalcium phosphate (β-TCP) in tricalcium phosphate/hydroxyapatite (TCP/HA) composites was investigated by X-ray diffraction, differential scanning calorimetry, thermogravimetry and scanning electron microscopy in this study. The current experimental results indicated that the calcining temperature for the complete phase transition from α-TCP into β-TCP increased with the increasing HA content in the composite. HA/β-TCP biphasic composites with initial Ca/P molar ratios of 1.571, 1.600 and 1.636 were synthesized. The particle coarsening occurred significantly in the process of calcination.